Search

The first aerobic protocol of direct transformation of p‐methoxybenzyl (PMB) ethers to carboxylic acids efficiently with Fe(NO3)3 ⋅ 9H2O and TEMPO as catalysts at room temperature has been developed. The reaction accommodates C−Br bond, terminal/non‐terminal C−C triple bond, amide, cyano, nitro, ester, and trifluoromethyl groups. Even highly selective oxidative deprotection of different benzylic PMB ethers has been realized. The reaction has been successfully applied to the total synthesis of natural product, (R)‐6‐hydroxy‐7,9‐octadecadiynoic acid, demonstrating the practicality of the method. Based on experimental studies, a possible mechanism involving oxygen‐stabilized benzylic cation has been proposed. [ABSTRACT FROM AUTHOR]

The kinetics of the liquid-phase oxidation of cumene (RH) with molecular oxygen in the presence of KMnO4 and N-hydroxysuccinimide (NHSI) is studied. An increase in the reaction rate when adding acetic acid is established. An synergistic effect of KMnO4 and NHSI in aerobic oxidation of RH is found. This can be associated with the formation of C-centered (R⦁) and O-centered (SINO⦁) radicals that participate in the chain initiation stage and the catalysis of the chain propagation stage by the SINO⦁ radical. [ABSTRACT FROM AUTHOR]

Catalytic desaturations are important strategies for the functionalization of organic molecules. In nature, flavoenzymes mediate the formation of α,β‐unsaturated carbonyl compounds by concomitant cofactor reduction. Contrary to many laboratory methods for these reactions, such as the Saegusa‐Ito oxidation, no transition metal reagents or catalysts are required. However, a molecular flavin‐mediated variant has not been reported so far. We disclose a photochemical approach for silyl enol ether oxidation, which leads to α,β‐unsaturated ketones (13 examples) in very good yields. The flavin catalysts are stable throughout the desaturation reaction, and we successfully applied them in a subsequent aerobic epoxidation by simply changing the reaction conditions. This protocol allowed us to directly convert silyl enol ethers into α,β‐epoxyketones in a one‐pot fashion (12 examples). Sequential flavin catalysis is not limited to one specific reactivity combination and can, inter alia, couple the photochemical oxidation with radical additions. We anticipate that flavin‐catalyzed desaturation will be applicable to other substrate classes and that its sequential catalytic activity will enable rapid substrate diversification. [ABSTRACT FROM AUTHOR]

Comprehensive Summary: Aerobic oxidation has been catching more and more attention because of its atom economy and environmental friendliness. Oxidation of diols is a challenge due to various oxidative products. Thus, highly selective aerobic oxidation affording specific products is of current interest. In this work, a combination of Fe(NO3)3·9H2O/TEMPO/KCl catalysis has been identified as an efficient recipe for the aerobic oxidation of 1,4‐diols affording γ‐butyrolactones under mild conditions. The reaction exhibits decent chemo‐ and regioselectivity of symmetrical and unsymmetrical 1,4‐diols. The optically active γ‐lactones may also be prepared from optically active 1,4‐diols without erosion of the ee via this method. Furthermore, this approach was successfully applied to synthesize NBP, a commercial drug. [ABSTRACT FROM AUTHOR]

Comprehensive Summary: Aerobic oxidation has been catching more and more attention because of its atom economy and environmental friendliness. Oxidation of diols is a challenge due to various oxidative products. Thus, highly selective aerobic oxidation affording specific products is of current interest. In this work, a combination of Fe(NO3)3·9H2O/TEMPO/KCl catalysis has been identified as an efficient recipe for the aerobic oxidation of 1,4‐diols affording γ‐butyrolactones under mild conditions. The reaction exhibits decent chemo‐ and regioselectivity of symmetrical and unsymmetrical 1,4‐diols. The optically active γ‐lactones may also be prepared from optically active 1,4‐diols without erosion of the ee via this method. Furthermore, this approach was successfully applied to synthesize NBP, a commercial drug. [ABSTRACT FROM AUTHOR]

The ease with which simple starting materials can be transformed into highly functionalized products has made oxidative N‐heterocyclic carbene (NHC) catalysis an area of significant interest. However, the use of stoichiometric amounts of high molecular weight oxidants in most reactions generates an undesired equivalent amount of waste. To address this issue, the use of oxygen as the terminal oxidant in NHC catalysis has been developed. Oxygen is attractive due to its low cost, low molecular weight, and ability to generate water as the sole by‐product. However, molecular oxygen is challenging to use as a reagent in organic synthesis due to its unreactive ground state, which often requires reactions to be run at high temperatures and results in the formation of kinetic side‐products. This review covers the development of aerobic oxidative carbene catalysis, including NHC‐catalyzed reactions with oxygen, strategies for oxygen activation, and selectivity issues under aerobic conditions. [ABSTRACT FROM AUTHOR]

3-Cyano-1-methyl-4-trifluoromethyl-3-pyrroline, as well as 4-cyano-1-methyl-3-trifluoromethyl- and 3-cyano-1-methyl-4-trifluoromethyl-2-pyrrolines were synthesized under DBU catalysis by heating of Z-3-cyano-4-ethoxy-1-methyl-4-trifluoromethyl-pyrrolidine in vacuo. 3-Cyano-1-methyl-4-trifluoromethyl-3-pyrroline undergoes redox disproportionation catalyzed by potassium tert-butoxide to form 2,4-bis(2-cyano-1-trifluoromethylprop-2-enylidene)-1,3-dimethyl-1,3-diazetidine and E-/Z-isomers of 3-cyano-1-methyl-4-trifluoromethylpyrrolidine. The same 1,3-diazetidine is formed by oxidation of 3-cyano-1-methyl-4-trifluoromethyl-3-pyrroline with atmospheric oxygen. Individual E- and Z-isomers of 3-cyano-1-methyl-4-trifluoromethylpyrrolidine were obtained by stereospecific 1,3-dipolar cycloaddition of E- and Z-isomers of 4,4,4-trifluorobut-2-enonitrile to N-methyl(methaniminio)-N-methylide generated in situ. [ABSTRACT FROM AUTHOR]

One of a widely used broad-spectrum industrial bactericidal and mildew prevention agents is 1,2-benzoisothiazolin-3-one (BIT). In present study, it was demonstrated that aerobic oxidative cyclization of 2‑mercaptobenzamide (MBA) and 2,2'-disulfanediyldibenzamide (DSBA) in the presence of Mn(OAc)2 as catalyst allowed to obtain BIT. The mechanism reaction was suggested. It was found that DSBA and MBA can be converted to the BITwith 99% yield at 1.0 mol % Mn(OAc)2 under 0.3 MPa of oxygen and 100°C for 8 h. Experimental data point that this protocol is both economical and environmentally friendly. [ABSTRACT FROM AUTHOR]

The hybrid periodic mesoporous organosilica (PMO) with APTES/DAR Schiff-based precursor 3-aminopropyltriethoxysilane (APTES) and 4,6-diacetylresorcinol (DAR) was synthesized in the presence of a structure-directing agent cetyltrimethylammonium bromide and tetraethoxysilane. Then, Pd (II) ions, as well as Pd nanoparticles, were incorporated inside the pore walls of the synthesized APTES/DAR-PMO. The PMO structure was characterized by HRTEM, FT-IR, TEM, FE-SEM, BET, SEM-EDX, low angle XRD, HADAF-mapping, TGA, and atomic absorption spectroscopy (AAS). Subsequently, the as-fabricated green heterogeneous nanocatalysts (Pd-NPs@APTES/DAR-PMO) was used as effective and sustainable catalysts for the aerobic oxidation of benzylic alcohols into their corresponding aldehydes in pure water A high Pd-NPs@APTES/DAR-PMO-catalyzed conversion level of the primary and secondary alcohols was demonstrated. Furthermore, the environmentally friendly catalyst showed outstanding stability, so that readily separated by centrifugation and reused for seven consecutive cyclic terms with good retention of high catalytic activities. [Display omitted] • Engineering the mesochannel of organosilica with Schiff base frameworks. • Design of Schiff base bisylil (APTES/DAR) as a bifunctional linker. • The presence Schiff base in surface of PMO stabilizes Pd(II) ions and Pd nanoparticles. • Pd-NPs@APTES/DAR-PMO is a promising catalyst for aerobic alcohols oxidation. [ABSTRACT FROM AUTHOR]

Novel Au nano-particle catalysts immobilized on both titanium(IV)- and alkylthiol-functionalized SBA-15 type ordered mesoporous silicate supports were developed. The bi-functionalized SBA-15 type support could be synthesized by a one-pot method. To the synthesized supports, Au was immobilized by the reaction of the alkylthiol groups on the supports with AuCl4−, following reduction with NaBH4. The immobilized amount and the formed structures and the electronic property of the Au species depended on the loading of alkylthiol. The moderate size (2–3 nm) nano particulate Au sites formed on Ti(0.5)-SBASH(0.5) were negatively charged. The aerobic alcohol oxidation activity of the catalysts depended on the loading of alkylthiol and the structure of the Au nano-particles. The non-thiol-functionalized catalyst (Au/Ti(0.5)-SBASH(0)) composed of the large (5–30 nm) and the higher thiol-loaded catalyst (Au/Ti(0.5)-SBASH(8)) composed of the small cationic Au species were almost inactive. The most active catalyst was Au/Ti(0.5)-SBASH(0.5) composed of the electron-rich Au nano-particles formed by the electron donation from the highly dispersed thiol groups. Styrene oxidation activity in the presence of 1-phenylethanol with O2 depended on the loadings of titanium(IV) on the Au/Ti(x)-SBASH(0.5). The titanium(IV) sites trapped the H2O2 generated through the alcohol oxidation reaction, and also contributed to the alkene oxidation by activating the trapped H2O2. [ABSTRACT FROM AUTHOR]

A low transition temperature mixture formed with 1‐butyl‐3‐(methoxycarbonylmethyl)imidazolium chloride and iron(III) chloride has proven to be an efficient catalyst for the synthesis of quinazolines following a sequence of condensation‐cyclization‐oxidation reactions. The protocol is simple and effective for coupling 2‐acylanilines and benzylamines to form nitrogen containing heterocycles with moderate to excellent yields (up to 93 %), being possible to perform the reaction in preparative scale. The functionalized imidazolium salt is crucial for the activation of the reagents under solvent‐free conditions, and the presence of iron in the catalyst mediates the oxidation step with atmospheric oxygen. These features make the presented procedure better, from an environmental point of view, than other processes previously described. For this comparison, different "green" metrics have been used, such as atom economy, stoichiometric factor, reaction mass efficiency, E‐factor, and EcoScale. [ABSTRACT FROM AUTHOR]

The metal organic framework {[Cu2(CN)3(phen)3]5H2O} MOF1- bicarbonate system was investigated as an efficient catalyst for aerobic oxidation of 2, 6-di-tert-butylphenol (2,6- DTBP). The catalytic system showed very efficient catalytic behavior for the oxidation of selective coupling of 2,6- DTBP to 3,3′,5,5′-tetra-tert-butyl-4,4′-diphenoquinone (DPQ) in excellent yield. The influence of reaction parameters on the selective oxidation of 2, 6-DTBP to DPQ had been investigated. Photoluminescence probing technology of Disodium salt of terephthalic acid as well as scavenging experiments revealed the creation of the hydroxyl radicals as the main active oxidation radicals produced by the MOF1/O2/basic bicarbonate system. The oxidation reaction mechanism was also discussed. The recycled catalytic system retained its activity for eight successive runs.

Direct hydroxylation of benzene to phenol with dioxygen is a green route for synthesis of phenol. The higher bonding energies of C–H in benzene and O–O in dioxygen make metal-free catalysis a challenge. A novel metal-free catalyst of quinone-cylcohexanone-formaldehyde polymer was rationally designed and prepared. The polymer was characterized with FT-IR, XRD, Raman, SEM, 13C NMR and XPS. Abundant oxygen functional groups of cyclic ketonic, quinone carbonyl and hydroquinone were found on the surface of polymer. The catalytic performances for hydroxylation of benzene to phenol with dioxygen over the metal-free catalyst were investigated and a phenol yielding of 11.4% was achieved. Moreover, the reaction mechanism was proposed. [ABSTRACT FROM AUTHOR]

• Design of a highly water dispersible/magnetically separable TEG-Imidazolium Functionalized TEMPO. • Stable colloidal dispersion in water and high performance in the aerobic oxidation of various types of alcohols. • The catalyst exhibited high performance dual-adjustable-selectivity in the oxidation of primary alcohols. • Highly recoverable stable magnetic colloidal dispersion in water using a unique double-separation-strategy. • Synergistic catalysis between functionalized imidazolium bromide and TEMPO in the same solid. It is expected that incorporation of 2, 2, 6, 6-tetra-methyl piperidine- N -oxyl radical (TEMPO) and an imidazolium bromide bearing hydrophilic triethylene glycol (TEG) groups on Fe 3 O 4 @SiO 2 core–shell may not only result in a novel highly water-dispersible/magnetically separable multi-functional catalyst system for metal-free aerobic oxidation of alcohols, which operates through a synergistic relay pathway, but it could potentially provide a strong platform for simultaneous separation and recycling of all components. The catalyst was prepared by anchoring TEMPO moieties onto a magnetic core–shell Fe 3 O 4 @SiO 2 functionalized with an ionic liquid bearing TEG groups. The materials was characterized using transmission electron microscopy, Fourier transform infrared spectroscopy, nitrogen adsorption–desorption isotherms, thermal gravimetric analysis, and elemental analysis. The performance of the catalyst was evaluated and quantitatively measured in the aerobic oxidation of alcohols in water. The catalyst exhibited excellent and stable colloidal dispersion in water and high performance in the aerobic oxidation of various types of alcohols under metal- and halogen-free reaction conditions. As hypothesized, strong synergistic effect between functionalized components was seen in the described reaction. The catalyst displayed excellent dual-adjustable-selectivity in the oxidation of primary alcohols to either the corresponding aldehydes or carboxylic acids by tuning the reaction solvent and/or reaction time and excellent recycling behavior through a "double-separation-strategy ". [ABSTRACT FROM AUTHOR]

An unprecedented catalytic system consisting of diselenides, Selectfluor and visible light has been developed for the one‐pot synthesis of oxazole acetals from N‐propargylamides and alcohols. This system shows the processes of cyclization, aromatization and acetalization, resulting in the construction of multiple carbon‐oxygen bonds. These transformations demonstrate the excellent compatibility of visible‐light promotion with organocatalytic oxidative carbon–oxygen bond formations using air as the terminal oxidant. [ABSTRACT FROM AUTHOR]

An aerobic dehydrogenation of nitrogen‐containing heterocycles catalyzed by Grubbs catalyst is developed. The reaction is applicable to various nitrogen‐containing heterocycles. The exceptionally high functional group compatibility of this method was confirmed by the oxidation of an unprotected dihydroindolactam V to indolactam V. Furthermore, by taking advantage of the oxygen‐mediated structural change of the Grubbs catalyst, we integrated ring‐closing metathesis and subsequent aerobic dehydrogenation to develop the novel assisted‐tandem catalysis using molecular oxygen as a chemical trigger. The utility of the assisted‐tandem catalysis was demonstrated by the concise synthesis of N‐containing fused heteroarenes including a natural antibiotic, pyocyanine. [ABSTRACT FROM AUTHOR]

The immobilization of H5PV2Mo10O40 polyoxometalates (POMs) in the in the mesoporous channel-type metal–organic framework (MOF), NU-1000, via simple impregnation method is reported here. Characterization of the composite PV2Mo10@NU-1000 activated by supercritical CO2 revealed that the POMs occupy the mesopore. Upon heating as low as 40 °C in the absence of bulk solvent, the POMs migrate to the micropore. However, the presence of solvent, such as cyclohexane, impedes this transformation. The material was active for the aerobic oxidation of the mustard gas simulant, 2-chloroethyl ethyl sulfide (CEES), in cyclohexane using isobutyraldehyde a sacrificial reductant and O2 as the oxidant. The activity of the POM allowed for efficient oxidation of CEES in the dark and in air. Immobilization of the POM in the MOF was found to improve the initial turnover frequency compared to the POM itself. Further, the POM catalyst was found to be unstable under the chosen reaction conditions and no activity was found upon washing and reusing the POM. As a composite PV2Mo10@NU-1000, the POMs retained their catalytic activity and allowed for recycling of the catalytic material. [ABSTRACT FROM AUTHOR]

Described here is a new and viable approach to achieve Pd catalysis for aerobic oxidation systems (AOSs) by circumventing problems associated with both the oxidation and the catalysis through an all‐in‐one strategy, employing a robust metal–organic framework (MOF). The rational assembly of a PdII catalyst, phenanthroline ligand, and CuII species (electron‐transfer mediator) into a MOF facilitates the fast regeneration of the PdII active species, through an enhanced electron transfer from in situ generated Pd0 to CuII, and then CuI to O2, trapped in the framework, thus leading to a 10 times higher turnover number than that of the homogeneous counterpart for Pd‐catalyzed desulfitative oxidative coupling reactions. Moreover, the MOF catalyst can be reused five times without losing activity. This work provides the first exploration of using a MOF as a promising platform for the development of Pd catalysis for AOSs with high efficiency, low catalyst loading, and reusability. [ABSTRACT FROM AUTHOR]

Set of [Ru(η6‐cymene)(R)XCl] (R=L1SnCl, L1GeCl L2PPh2, X=Cl or SnCl3, L1=[2‐(CH2NEt2)‐4,6‐(tBu)2C6H2]−, L2=2,6‐iPr2‐C6H3‐NH−) catalysts was tested in aerobic oxidations of primary amines. The activity of studied catalysts depends on the charge of the Ru atom that has been influenced either by donating ligands R or by character of X. Typical Ru/P catalyst [Ru(η6‐cymene)(L2PPh2)Cl2] (3) with least negative charge on the Ru atom has been observed as the most effective. The design of the phosphine ligand L2 containing amino‐phosphine PNH moiety provided efficient anchoring of complex 3 to silica gel via hydrogen bonding of the PNH functional group to SiO2 to give heterogeneous catalyst 3‐silica. This complex has been also efficiently tested in aerobic oxidation as recyclable catalyst with cumulative TON up to 6930. [ABSTRACT FROM AUTHOR]

Catalyzed by commercially available (PhTe) 2 , molecular oxygen could be utilized as the mild, cheap and safe oxidant for oxidative deoximation reactions under solvent-free conditions. As the first report on organotellurium-catalyzed deoximation reaction, this work not only provides an efficient deoximation method, but also discloses new features of tellurium catalyst different from those of the organoselenium catalysts. [ABSTRACT FROM AUTHOR]

The aerobic Cu/ABNO catalyzed oxidative coupling of alcohols and amines is highlighted in the synthesis of amide bonds in diverse drug‐like molecules (ABNO=9‐azabicyclo[3.3.1]nonane N‐oxyl). The robust method leverages the privileged reactivity of alcohols bearing electronegative hetero‐ atoms (O, F, N, Cl) in the β‐position. The reaction tolerates over 20 unique functional groups and is demonstrated on a 15 mmol scale under air. Steric constraints of the catalyst allow for chemoselective amidation of primary amines in the presence of secondary amines. All catalyst components are commercially available, and the reaction proceeds under mild conditions with retention of stereocenters in both reaction partners, while producing only water as a by‐product. [ABSTRACT FROM AUTHOR]

[Display omitted] • Co nanoclusters were in situ formed in aerobic oxidation of cis -cyclooctene. • Cyclooctene dimer oxide is formed to stabilize the clusters as a surfactant. • Efficient for soluble Co clusters in aerobic oxidation of α-C H of ethylbenzene. • TON of acetophenone yield on Co clusters is 960 times more active than Co salt. • In situ formed Co nanocluster is extended to aerobic oxidation of cyclohexene. Aerobic oxidation of α-C H bond of organic compounds to valuable chemicals is widely investigated in both fundamental research and industry. Due to the good stability of molecular oxygen, severe reaction conditions are generally required. Herein, by in situ synthesis we used molecular oxygen to induce cobalt nanoclusters with the sensitive catalysis in mild selective oxidation. The cobalt containing clusters with an average diameter around 0.9 nm are in situ prepared in the presence of cis -cyclooctene epoxidation and cyclooctene dimer oxide is formed at the interface to stabilize Co clusters with electron donation as an oil-soluble surfactant. The soluble clusters exhibit high activity in selective oxidation of α-C H bond of ethylbenzene into acetophenone and turnover number (TON) reaches about 7 × 104 during 50 h' reaction at 373 K, which is around 960 times more active than the one using CoCl 2 salt as the catalyst, resulting from efficient mass transportation, π bond interaction and oxygen gas activation. Extended work based on this understanding demonstrates that cobalt nanoclusters also effectively catalyze aerobic oxidation of cyclohexene. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Copper as catalyst, without nitroxyl radicals and ligands. • Molecular oxygen as the sole oxidant at room temperature. • Gram-scale synthesis. Abstract Chemoselective oxidative synthesis of N -(2-aminophenyl)imines from 2-amino- N -benzylanilines was accomplished through combined use of O 2 (air) and copper salt. This transformation was performed at room temperature, and the mild oxidation was efficient and chemoselective without using nitroxyl radicals and ligands. [ABSTRACT FROM AUTHOR]

Laccase/DDQ as a new bioinspired quinone-based cooperative catalytic system was used for the biomimetic aerobic oxidative synthesis of 2-substituted quinazolines and Hantzsch pyridines from the oxidative cyclocondensation of 2-aminobenzylamine and aldehydes and the oxidative aromatization of 1,4-dihydropyridines, respectively. The products were obtained in good to high yields in a phosphate buffer (0.1 M, 12.5 mL, pH 4.5) and acetonitrile (4 vol%) mixture as a solvent. These methods are more eco-friendly, efficient, simple, and practical than other currently available ones because of mild reaction conditions and because they are free from any halide and toxic and expensive transition metals. Therefore, these methods can be applied in pharmaceutical and other sensitive synthetic procedures. Image 1 [ABSTRACT FROM AUTHOR]

[Display omitted] Developing efficient heterogeneous catalysts for the aerobic oxidation of C–H bonds using oxygen molecule as an oxidant to produce value–added aryl ketones is a challenging task. In this study, a series of cementite–iron–carbon composites (referred to as Fe–C–T, where T represents the pyrolysis temperature) were synthesized using a metal–organic–framework–mediated sacrificial template strategy. The Fe–C–T composites consist of highly dispersed Fe/(Fe 3 C or Fe 2 O 3) nanoparticles surrounded by graphitic carbon on porous carbon supports. Under mild reaction conditions (1 atm of O 2 pressure, 353 K, 12 h), with tert–butyl hydroperoxide (0.25 equiv.) as the initiator in a green solvent water, the prepared Fe–C–973 achieved a high conversion of 98.4 % for ethylbenzene and a selectivity of 98.7 % for acetophenone. This performance was markedly superior to the comparable Fe–C–873 and Fe–C–1073, as well as the commercially available Fe–based catalysts. Kinetic studies revealed that the catalytic system followed first–order kinetics for the substrate ethylbenzene, and the activation energy over Fe–C–973 was remarkably low of 40.4 kJ/mol. The highly distributed Fe 3 C nanoparticles embedded in the porous carbon framework were identified as the most active sites for the reaction. [ABSTRACT FROM AUTHOR]

[Display omitted] • Aerobic oxidation of cyclooctane and linear hydrocarbon is reported using Fe(BTC) metal organic framework. • The reaction conditions are milder compared to literature reports. • Aerobic oxidation is performed without radical initiators or peroxides. Aerobic oxidation of hydrocarbons is one of the research fronts in organic chemistry as well as in chemical engineering. In this aspect, many efforts are devoted to develop heterogeneous catalysts that can convert hydrocarbon to its corresponding alcohol/ketone (ol/one) with selectivity more than 90%. However, achieving this target becomes difficult due to possible secondary reactions of initially formed ol/one mixture. Hence, this study aims to report the catalytic activity of Fe(BTC) (BTC: 1,3,5-benzenetricarboxylate) and tetrabutylammonium bromide (TBAB) in aerobic oxidation of cyclooctane at 73% conversion to its respective ol/one with 84% selectivity after 24 h at 120 °C in the absence of any radical initiators. Interestingly, the selectivity of ol/one is higher than 90% at cyclooctane conversion around 20% under present reaction conditions. Reusability and leaching experiments demonstrate the stability of Fe(BTC) during the oxidation reaction. Furthermore, the present catalytic system can also be extended to oxidize other linear hydrocarbons to their respective ol/one products with the selectivity ranging between 88–97 %. [ABSTRACT FROM AUTHOR]

Carboxylic functionalized β‐carbolines were successfully synthesized in good to excellent yields and high selectivity under mild conditions by aerobic oxidation in the presence of NHPI and transition metal salt using molecular oxygen as an oxidizing agent. A variety of derivatives of fascaplysin thus are available for structure‐bioactivity investigations. Carboxylic functionalized β‐carbolines have been synthesized in good to excellent yields and high selectivity by oxygen in the presence of NHPI and transition metal salt under mild conditions [ABSTRACT FROM AUTHOR]

Oxidative coupling of primary amines to imines has been achieved by using a water soluble cobalt complex as catalyst and air as the oxidant at near ambient conditions. Aromatic, heteroaromatic and aliphatic amines were successfully converted to the corresponding imines with yields of up to 96 %. A 20 gram scale reaction for the synthesis of imine from benzylamine in good yield is also demonstrated with this method. The catalyst has been found to be reusable with up to five cycles. It is highly efficient, gives a turnover number (TON) of up to 128, and shows chemoselectivity with the only byproducts being water and ammonia. Control experiments and mechanistic studies indicate that the CoII/CoIII catalytic cycle is responsible for these oxidative transformations. Some of the reactive intermediates of this reaction have also been isolated and structurally characterized. Co operation: Catalytic activity of the water soluble N,N′‐bis(2′‐pyridinecarboxamide)‐1,2‐benzene cobalt complex for oxidation of amines to imines is reported. Reactions occurred at near ambient conditions by using air as the sole oxidant and water as solvent. Ease of preparation of the catalyst using an inexpensive ligand and cobalt salts, its water solubility and reusability are additional interesting features of this methodology. [ABSTRACT FROM AUTHOR]

Aerobic oxidation of cyclohexane, propane, ethane, and methane to the corresponding alcohols was investigated over an Au55 gold nanoparticle with icosahedron symmetry using density functional theory. Reaction mechanisms were elucidated and activation barriers for catalytic C H bond cleavage and corresponding alcohols’ formation were estimated. Furthermore, on the basis of the reaction rate constants calculated for realistic reaction temperatures, the relative reaction rates for each alkane hydroxylation were discussed. The catalyst selectivity was investigated for the formation of primary and secondary alcohols. All reaction mechanisms for alkane hydroxylation are compared with the catalytic dissociation of dioxygen molecule over gold nanoparticle surface, which is an important precursor reaction for aerobic oxidation. We have further investigated overoxidation reaction mechanisms leading to formation of ketones. Our results are compared with experimental findings to provide important guidelines for the tuning of catalytic reactions towards the desired products and reaction conditions. [ABSTRACT FROM AUTHOR]

A convenient and efficient copper-catalyzed aerobic oxidation of primary amines to aryl nitriles was described. Various benzylic and allylic amines were selectively oxidized to the corresponding nitriles in high yields using CuBr 2 /NMI as the catalyst and O 2 as the oxidant. The oxidation reaction profiles monitored by 1 H NMR disclosed the scenario of the reaction path as well as the role of the additives. The addition of NMI increased the rate of reaction and suppressed the hydrolysis and the deamination. [ABSTRACT FROM AUTHOR]

Abstract: A mild and selective C(sp3)−H aerobic oxidation enabled by decatungstate photocatalysis has been developed. The reaction can be significantly improved in a microflow reactor enabling the safe use of oxygen and enhanced irradiation of the reaction mixture. Our method allows for the oxidation of both activated and unactivated C−H bonds (30 examples). The ability to selectively oxidize natural scaffolds, such as (−)‐ambroxide, pregnenolone acetate, (+)‐sclareolide, and artemisinin, exemplifies the utility of this new method. [ABSTRACT FROM AUTHOR]

HNO 3 was demonstrated to be an effective catalyst for aerobic oxidation of benzylic sp 3 C H bonds under additive-free conditions. A series of isochromans, xanthenes and fluorenes underwent this transformation to give the targeted products in low to high yields under the catalysis of HNO 3 , which provided an effective method for the synthesis of the synthetically and biologically valued isochromanones, xanthones and 9-fluorenones. [ABSTRACT FROM AUTHOR]

[Display omitted] • Provide a highly efficient and solvent-free system of cobalt/NHPI/IL-catalyzed aerobic oxidation of hydrocarbons. • Reach a reasonable understanding of the catalytic system, wherein a solution of reversed vesicles being formed. • The efficiency was influenced by both the composition of microdomains and the structure of IL at the interface. A highly efficient and solvent-free system of cobalt/NHPI-catalyzed aerobic oxidation of hydrocarbons was developed using imidazolium-based ionic liquid (IL) as an additive. These amphipathic ILs were found self-assemble at the interface between the organic hydrocarbons and the aqueous phase of catalyst combination (Co/NHPI), with forming a solution of reversed multilamellar vesicles for catalysis. The initial reaction rate was influenced by both the composition of microdomains and the structure of IL launched. Consequently, a proper water content (χ H2O) of wet IL was requisite to reach the optimum reactivity. Besides, the interfacial boundary between aqueous and organic phase composed by C2-alkylated imidazolium ILs, such as [bdmim]SbF 6 and [C 12 dmim]SbF 6 , not only has ternary aggregates (hydrocarbons/IL/H 2 O) of higher stability but renders O 2 a faster diffusion rate and higher concentration, thereby offering a high reactivity of the protocol towards hydrocarbon oxidation. [ABSTRACT FROM AUTHOR]

Range separated density functionals capture accurately the dynamics of PdIII–O 2 superoxide formation by revealing the non-bonding (anagostic) and bonding interactions involved in the process. [Display omitted] • Aerobic oxidation of Pd complexes in C−C coupling reactions pass through the formation of PdIII – Superoxo intermediate and the crucial step of O 2 addition to Pd center bearing tetradentate pyridinophane ligands have been investigated with DFT. • Among several functionals tested range separated functionals, particularly M11 describes the dynamics of the process accurately. • Asymmetric substitutions favour O 2 addition to Ni, Pd and Pt centers by decreasing the steric nature (bis anagostic interactions) of N 4 ligand than symmetirc substitutions. Aerobic oxidative C C coupling catalyzed by dimethyl PdII center (L–[Pd]) bearing tetradentate pyridinophane (N 4) ligand L (L = N, N -dimethyl-2,11-diaza[3.3]-(2,6)pyridinophane) has been investigated using density functional theory (DFT) computations. In Pd-catalyzed aerobic oxidation processes, the interaction of dioxygen with PdII center is a crucial step. Computations reveal that the reactant dimethyl PdII complex L–[Pd] has anagostic interactions (4 × Pd···H ∼ 2.60 Å) in total agreement with reported experimental NMR downshift values and these interactions play a significant role in the formation of PdIII – Superoxo intermediate which is less probed. While oxygen approaches the reactant, PdII center becomes PdIII allowing axial amine coordination. This pushes two protons (C sp 3 – H) away from Pd center weakening the two anagostic interactions. The other two anagostic interactions are intact at long ranges and at closer distances they weaken facilitating Pd – O bonding. The formation of the PdIII center in the PdIII – Superoxo were confirmed by reported EPR measurements. To understand this process, this key step has been modelled. Calculations have been performed with fourteen different density functionals (M06L, B3LYP, PBE0, M06, M11 to name a few) and different basis sets both in gas phase and in solvent medium. It is found that the range separated functionals, particularly M11 functional describe the process accurately and this is attributed to their efficiency of handling electron correlation at different ranges by including different percentage of Hartree-Fock exchange. The role of anagostic interactions M⋯H (M = Ni, Pd and Pt) in metal – superoxo species bearing symmetric and asymmetric substituted N 4 ligands have been investigated. These results clearly explain asymmetrically substituted N 4 ligands assist the simultaneous creation of M – O bonds at medium ranges and the weakening of bis anagostic (repulsive) M∙∙∙H interactions at short ranges. These findings suggest that intermediate stabilization in C C coupling processes mediated by transition-metal catalysts containing N 4 ligands depends critically on the strength of anagostic interactions. [ABSTRACT FROM AUTHOR]

A method for the aerobic cascade oxidation of cyclopentane-1,2-diones using metal porphyrins as catalysts, yielding hydroxydiacids 2 , ketoacid 3 and diketoacids 4 which are the intermediates of important biologically active compounds is reported. This method is operationally simple and can be employed under ambient conditions. [ABSTRACT FROM AUTHOR]

A catalyst comprising of catalytic cobalt(II) acetate/copper(II) acetate/DL-tyrosine with oxygen as the oxidant allows aerobic intramolecular C--O bond construction in [2-(pyrrolidin-1-yl)phenyl]methanol by free-radical promoted intramolecular selective functionalization of an (sp3)C--H bond by the alcohol, thus providing an environmentally friendly approach to 5H-benzo[d]pyrrolo[2,1-b][1,3]oxazine derivatives. [ABSTRACT FROM AUTHOR]

The aerobic oxidative cleavage of 1,2-diols using a heterogeneous catalyst only based on earth-abundant metals manganese and sodium is reported for the first time. This reusable catalyst cleaves a variety of substrates into aldehydes or ketones with high selectivity. The reaction requires small catalytic loadings and is performed under mild conditions using ambient pressure O2 or air as the oxidant while producing water as the only by-product. Mechanistic investigations reveal a monodentate, two-electron oxidative fragmentation process involving a MnIV species. The eco-friendly, innocuous catalyst is compatible with a wide range of functional groups and conditions, making it highly competitive with classical reagents, such as periodic acid or lead tetraacetate, as a preferred method for activated 1,2-diols. [ABSTRACT FROM AUTHOR]

An iron-catalyzed aerobic oxidation of (alkyl)(aryl)azinylmethanes has been developed leading to tertiary alcohols in moderate to good yields. Hock rearrangement was identified as a major side reaction leading to a complex mixture of undesired products. Addition of thiourea sometimes allows inhibiting this side reaction and steers the reaction towards the desired products. [ABSTRACT FROM AUTHOR]

In recent years, visible-light-driven organic reactions have been experiencing a significant renaissance in response to topical interest in environmentally friendly green chemical synthesis. The transformations using inexpensive, readily available visible-light sources have come to the forefront in organic chemistry as a powerful strategy for the activation of small molecules. In this review, we focus on recent advances in the development of visible-light-driven organic reactions, including aerobic oxidation, hydrogen-evolution reactions, energy-transfer reactions and asymmetric reactions.These key research topics represent a promising strategy towards the development of practical, scalable industrial processes with great environmental benefits. [ABSTRACT FROM AUTHOR]

ABSTRACT 2′,4′- p-Vinylbenzylideneriboflavin ( 2′,4′-PVBRFl) was prepared as a flavin-containing monomer and copolymerized with divinylbenzene and styrene or its p-substituted derivatives such as 4-acetoxystyrene, 4-vinylbenzyl alcohol, and 4-vinylbenzoic acid to give the corresponding non-functionalized and functionalized PS-DVB-supported flavins PS(H)-DVB-Fl, PS(OAc)-DVB-Fl, PS(CH2OH)-DVB-Fl, and PS(COOH)-DVB-Fl, respectively. PS(OH)-DVB-Fl was also prepared by hydrolysis of PS(OAc)-DVB-Fl under basic conditions. These novel flavin-containing insoluble polymers exhibited characteristic fluorescence in solid state, except PS(OH)-DVB-Fl, and different catalytic activities in aerobic reduction of olefins by in situ generated diimide from hydrazine depending on their pendant functional group. For example, PS(H)-DVB-Fl was found to be particularly effective for neutral hydrophobic substrates, which could be readily recovered by a simple filtration and reused more than 10 times without loss in catalytic activity. On the other hand, PS(OH)-DVB-Fl and PS(COOH)-DVB-Fl proved to be highly active for phenolic substrates known to be less reactive in the reaction with conventional non-supported flavin catalysts. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017, 55, 1706-1713 [ABSTRACT FROM AUTHOR]

Efficient and highly selective catalytic conditions for the aerobic autoxidation of methylarenes to benzaldehydes, based on N-hydroxyphthalimide (NHPI) and cobalt(II) acetate in 1,1,1,3,3,3-hexafluoropropan-2-ol (HFIP), were developed. The sustainable conditions enable a multigram scale preparation of benzaldehyde derivatives in high efficiency and with excellent chemoselectivity (up to 99 % conversion and 98 % selectivity). [ABSTRACT FROM AUTHOR]